Nitrous cheating stories are an enduring cornerstone of bench racing, so it’s no surprise that veteran squeeze guru Mike Thermos often brought up the topic during his presentation at the 2016 Advanced Engineering Technology Conference.
“There’s been a lot of cheating with nitrous,” says Thermos, who was one of the founders of Nitrous Oxide Systems (NOS) and is now head of Nitrous Supply. “I mean a .030-inch hole can get you tremendous horsepower.”
Thermos, along with Steve Johnson of Induction Solutions, offered a number of tips to those engine builders and aftermarket manufacturers in attendance. In a wide-ranging discussion that included a Q&A, topics such as compression ratio, cam specs, types of fuel, solenoid problems and types of nitrous systems were all covered. The duo also got into nitrous myths and misconceptions that may be keeping racers from utilizing a very efficient power adder. But cheating seemed to get everyone’s attention, if only because there are so many types of racing that prohibit its use.
Thermos was part of a small underground movement in the early days of hot rodding that tried nitrous and admits not everyone knew how to use it. “People used to think you just put nitrous in the motor,” remembers Thermos. “In the old days that’s what everybody did. The car would run like a scalded dog for 100 yards, go dead lean and burn the pistons. So it got a negative connotation.”
Of course, that’s because nitrous oxide — which is a chemical molecule consisting of two nitrogen atoms and one oxygen atom — is not a fuel; it’s an oxidizer.
“We learned over the years that the fuel is what made horsepower, not nitrous,” says Thermos, who actually started helping Top Fuel teams get their nitro engines lit properly. “Magnetos weren’t that powerful in those days; the spark wouldn’t jump the plug and they would be dropping cylinders. So we brought in a bit of gaseous nitrous using an adapter that went into the Enderle nozzle. We’d pee just a little bit of nitrous gas to get the cylinder to light, not to make power — the nitro made the power. We were extremely successful in those days, and then they banned nitrous.”
Trying to make power with nitro and nitrous is quite the challenge, reminds Thermos, with the potential for disaster.
“Nitro releases its oxygen at the same temperature, 570 degrees, as nitrous,” says Thermos. “When you run them together you get a ton of oxygen and start burning up parts. A lot needs to be learned.”
Modern nitrous kits introduce nitrous and additional fuel at the same time through one of two systems: plate and port injection. A plate system sits between the carburetor and intake manifold and consists of two spray bars that run across the plenum opening—one bar each for the fuel and nitrous. As an oxidizer, the nitrous provides the added oxygen to burn the extra fuel and make more power. In a port system, unique nozzles that blend the nitrous and fuel are installed in each intake port.
Metering the system are different sized jets located in the nozzles or at the spray bars. The larger the jet, more fuel and nitrous get introduced into the engine. Controlling the flow to the nozzles or spray bars are electric solenoids that when activated by the driver or instructions from a computer open valves to allow flow of fuel and nitrous.
In discussing the pros and cons of plate versus port injection, Thermos and Johnson stressed that both efficiency, cost and even manifold design factors come into play.
“With plates, if you try to build a ton of nitrous and fuel down the intake, distribution becomes an issue,” says Thermos, who was one of the early pioneers of Pro Mod. “Nitrous comes out at 800 psi. Fuel comes out at 6 psi.”
“In a nitrous plate system, we always look at the fact that certain engine combinations are more favorable to a plate,” adds Johnson. “If you’re looking for lower horsepower, say 250 to 300 horsepower and below, you’re going to get away with it a lot more because individual cylinders aren’t going to show themselves as much as if you go up to 400, 500 and 600 horsepower. The next step is port injection.”
Nitrous customers are always interested in the horsepower ratings of a nitrous system. As mentioned before, changing the jet sizes determines the amount of power increase. But in the just the past few years there’s been a reversal of tuning strategy with jet sizes.
“The tune-up has flipped over,” says Johnson. “There was a day when the fuel jet was bigger than the nitrous jet. Today it’s rare if you ever see that. We leaned the systems down to get all the fuel out of them.”
Induction Solutions has a policy to flow test every system built in the shop. They start by flowing the nitrous side, gathering the data and making calculations that represent the power potential.
“Then we wet flow the fuel side of the system until we get the right pounds per hour to match the nitrous jet,” says Johnson. “One of the advantages of flowing the system is you’ll get more accurate numbers on your tune-up.”
Here are a few more takeaway tips, tricks and quotes from the presentation:
Best Fuel To Use With Nitrous?
“We find the best results on good old racing gasoline,” says Thermos. “There is more interest in E85. Because of the cooling effect with alcohol or methanol, it gets so cold it doesn’t want to vaporize. (Thermos had earlier explained that nitrous oxide is stored as a liquid, and when released under pressure into the intake manifold it drops to -127 degrees F.)
Is Nitrous Hard On Parts?
“People have stayed away from nitrous because they thought it was voodoo and it tore parts up,” says Johnson. “Simply it’s not nitrous that hurts parts, it’s people that hurts parts.”
Johnson says the primary culprit is a poor tuneup, along with inadequate parts and improper engine combinations. The industry has responded with improved piston rings and other parts along with a better understanding of the tune-up, so failures occur less frequently.
Okay, Which Is Better: Plate Or Port Injection?
“First, ask how much horsepower are you looking for? Then, are there any rules that have to be addressed. Finally, are there budget limitations,” says Johnson. “A plate is less expensive and easier to install. But ultimately, if the guy doesn’t have rules or a budget to stop him, a direct-port system is the best way to do it. It’s more reliable and you have the ability to compensate individual cylinders. Although plate systems have evolved. We have guys in plate-specific classes putting 550 to 650 horsepower through a plate system into a common plenum.”
Ignition Timing Retard
Thermos teamed with SuperFlow many years ago to analyze cylinder pressures with nitrous. Accuracy was in the range of one-tenth of a degree of crank rotation.
“With nitrous we sped up the burning rate to the fuel,” says Thermos. “And we had to bring that sweet spot back to 15 to 20 degrees ATDC where it made peak cylinder pressure. Some people fear that when you retard the timing, you’re taking away power. You’re actually adding power to get that sweet spot back.”
Dyno Testing With Nitrous
“You may notice that brake specific (BSFC) will go way down,” says Thermos. “If you’re running .40 and hit the nitrous, it could go down to .28. You might say, ‘boy, that’s an efficient motor.’ But what people don’t realize, when nitrous reaches 570 degrees F, the oxygen atom flies off, which gives off a tremendous amount of energy, and dynos aren’t calibrated for that. You end up getting a skewed brake specific.”
What’s The Ideal Compression Ratio For Nitrous?
“There’s a little more to it than just a number. If I had to give a number, and we’re talking about a racing engine, I say around 13.5:1,” says Johnson. “If you get more involved with cylinder heads and combustion chamber design, you could run over 14:1. If you have a jet-limited class, sometimes you can favor more compression.”
“You got to get the heat out,” says Johnson. “So lobe separation gets tighter and duration on the exhaust gets longer.”
Are Progressive Controllers Hard On Solenoids?
“It’s what I call an internet myth,” says Johnson, noting solenoid materials have improved but the real offenders are high line pressure and long duration of pressure, like leaving the system on while in the staging lane. “The hardest job for a nitrous solenoid is that initial opening and getting off the seat. The higher the pressure, the harder it is to do that. Even with high horsepower kits, we only see 825 to 875 psi to start. There are people wanting to run 1,000 or 1,050 psi. You actually gain better density at 850.”
Bad Electrical Connections
“I may work on the nitrous for free [at the track], but I charge $100 an hour if I have to work on your electrical system,” warns Johnson, adding that maintaining a good source of power, good ground connections and good relays are key to keeping the system happy. “A high percentage of tech calls we find problems are basically traced to poor voltage to the solenoid.”
Okay, Mike, Tell Us A Cheating Story
“I put a 2-pound nitrous bottle in an empty battery case,” says Thermos, who in the past has talked about seeing nitrous hidden in brake boosters.”
Thermos also recalls there was a remote switch that the push-truck driver controlled.
“Even the driver might not know he has nitrous,” quips Thermos. “He could have put him into the wall!”